1. Field of the Invention
The present invention relates to a camera, and more particularly to a camera which performs auto-focusing control by a passive system.
2. Description of the Related Art
For cameras which perform auto-focusing control in range finding, focus determination and the like by a passive system, what is provided with a device for emitting an auxiliary light for auto-focusing use is proposed because insufficient luminance of the subject prevents auto-focusing control from appropriately functioning. Also is proposed such a device using an electric flash as the source of the auxiliary light (Japanese Patent Application Publication Nos. 55-15154, 59-201009, 2000-111791 and 2000-338386, Japanese Patent No. 3139067 and so forth).
Conventionally, whether to emit an auxiliary light for auto-focusing is judged on the basis of the result of photometry for AE control, but there is a problem that the difference between the range of the subject to be automatically focused on and that of the subject of AE sometimes makes that judgment inappropriate. There is another problem that, where a device which emits the auxiliary light has a temperature characteristic (especially an electric flash is affected by the temperature characteristic of the main capacitor), the amount of auxiliary light emission varies with the ambient temperature, and accordingly may not be always appropriate. There is still another problem that, whereas one of known shooting modes is a night scene portrait mode in which a portrait is taken with a background of night scene, if whether or not to emit an auxiliary light is judged under the same conditions as the usual light emitting mode, auxiliary light emission is prevented by the luminous energy of the background of the subject person, and the background tends to more easily come into focus.
An object of the present invention, attempted in view of these circumstances, is to provide a camera capable of appropriate control of auxiliary light emission for auto-focusing according to the situation.
In order to attain the object stated above, the present invention is directed to camera, comprising: a sensor having a plurality of light receiving elements which receive light from a subject in a range-finding area; an auto-focusing controller which performs auto-focusing control according to an output of the sensor; an auxiliary light emitting device which emits auxiliary light for auto-focusing use toward the subject; a sensor sensitivity switching device which switches sensitivity of the sensor between a high level and a low level; a judging device which causes the sensor to receive light from the subject in a state where the sensitivity of the sensor is set in the high level, and judges according to the output of the sensor whether or not the auxiliary light should be emitted; and a control device which, if the judging device judges that the auxiliary light should be emitted, causes the sensor sensitivity switching device to switch the sensitivity of the sensor to the low level and causes the auxiliary light emitting device to emit the auxiliary light.
According to the present invention, since it is judged whether or not to emit an auxiliary light on the basis of the output of the sensor used for auto-focusing control, the judgment can be made on the basis of the luminance of the subject to be focused on. Furthermore, as the sensor is made more sensitive when judging whether or not an auxiliary light is required, the judgment can be made in a short period of time. Also, as the sensor is made less sensitive when the auxiliary light is emitted, saturation of the sensor output or similar trouble can be prevented and at the same time accurate focusing control can be performed even where the subject is at a short distance.
The present invention is also directed to a camera, comprising: a sensor having a plurality of light receiving elements which receive light from a subject in a range-finding area; an auto-focusing controller which performs auto-focusing control according to an output of the sensor; an auxiliary light emitting device which emits auxiliary light for auto-focusing use toward the subject; a temperature measuring device which measures a temperature within the camera; and a light emission control device which controls, according to the temperature measured by the temperature measuring device, at least one of duration and level of an emission of the auxiliary light so that an amount of the auxiliary light emitted from the auxiliary light emitting device is kept substantially constant.
According to the present invention, since the duration or the level of the emission of the auxiliary light is controlled on the basis of the temperature within the camera, the auxiliary light can be emitted in a steady amount without being affected by the temperature.
The present invention is also directed to a camera, comprising: a sensor having a plurality of light receiving elements which receive light from a subject in a range-finding area; an auto-focusing controller which performs auto-focusing control according to an output of the sensor; an auxiliary light emitting device which emits auxiliary light for auto-focusing use toward the subject when luminance of the subject is darker than a certain level; a shooting mode setting device which sets a desired shooting mode out of a plurality of shooting modes including a night scene portrait mode; and a light emission control device which, when the night scene portrait mode is set by the shooting mode setting device, causes the auxiliary light emitting device to emit the auxiliary light under a brighter condition than when any other shooting mode is set.
According to the present invention, when the shooting mode is the night scene portrait mode, the auxiliary light is emitted under a brighter condition than when any other shooting mode is set, the auxiliary light is thus emitted even when the background is relatively bright, and accordingly inadvertent focusing on some element in the background or similar trouble can be prevented.
The present invention is also directed to a camera, comprising: a sensor having a plurality of light receiving elements which receive light from a subject in a range-finding area; an auto-focusing controller which performs auto-focusing control according to an output of the sensor; an auxiliary light emitting device which emits auxiliary light for auto-focusing use toward the subject; a light emission counting device which judges whether a number of times the auxiliary light is emitted by the auxiliary light emitting device has reached a predetermined maximum number of times; and a control device which causes the auxiliary light emitting device to emit the auxiliary light so as to acquire an output value from the sensor, wherein if a desired output value is obtained from the sensor before the number of times the auxiliary light is emitted reaches the maximum number of times, the control device ends the emission of the auxiliary light, wherein if the number of times the auxiliary light is emitted reaches the maximum number of times before the desired output value is obtained from the sensor, the control device acquires the output value from the sensor at that point of time.
According to the present invention, when a sufficient output fails to be obtained from the sensor even if the auxiliary light is emitted a predetermined maximum number of times, auto-focusing control is performed on the basis of the sensor output at that point of time instead of deeming the failure as a focusing error, so that the frequency of focusing errors can be reduced.